It didn't do Vladimir Putin any political harm being photographed topless and muscular. But then again Putin was fishing in the wilderness, not – as was newly resigned Republican congressman Chris Lee – apparently trawling for extra-marital fun on a "women seeking men" internet forum.

The 46-year-old New York representative resigned hours after the Gawker website reproduced a seemingly self-posed mobile phone picture of Lee's admittedly trim torso, which he sent to a woman on the Craigslist site, claiming to be a "very fit fun classy guy" who was divorced.

Lee – in fact married with a son – said he in a statement was stepping down: "I regret the harm that my actions have caused my family, my staff and my constituents. I deeply and sincerely apologise to them all. I have made profound mistakes and I promise to work as hard as I can to seek their forgiveness."

The salutary tale for all politicians in an age of instant communication began in mid-January when a 34-year-old single woman placed a post on Craigslist's "women seeking men" section, inviting response from "financially & emotionally secure" males. Using his own Gmail account Lee replied, describing himself as divorced and 39, and later sending the shirtless shot. There followed some mild email flirtation, with the woman mockingly asking whether the picture came from "a JC Penny ad" and Lee describing a supposed recent disastrous date.

Lee's downfall came when the woman carried out a web search and discovered her internet suitor's identity, real marital status and age. She forwarded the correspondence to Gawker, which subsequently published it.

Presented with the evidence, Lee's spokesman initially insisted the politician's email account had been hacked and that he was "happily married".

But several hours later he had resigned. "I have to work this out with my wife," Lee told a Fox News reporter.

Lee's resignation came just a month after his fellow Republicans formally took control of the House of Representatives from the Democrats.

Lee was a member of two powerful House committees – the tax-drafting ways and means and financial services. He was first elected to the House of Representatives in 2008 and was re-elected in November.